The demand for "faultless" signal transmission in the field of telecommunications is very high in certain cases. For instance, in the aforesaid digital transmission links of a switching core of a telecommunications switching centre or exchange the bit error rate (BER) must be extremely low.
Reliability can be further improved by tripling the transmission, wherein three separate links are used, with each link transmitting the same information. By mutually comparing the signals/bits received on the three links and applying the majority decision, it is often possible to sort out the majority of occurrent bit errors when the three sets of received information are not identical.
However, it is necessary for the three signals to arrive simultaneously at the point at which the majority decision shall be taken. However, the requirement of exact simultaneity may be difficult to achieve for several reasons. The time deviation or so-called skew in parallel signal transmissions can occur in the electronic components and also in the signal transmission lines. Skew in electronic components can be minimized by suitable construction of the components.